1. Field of Invention
The present invention relates to a sensor unit incorporating a sensor to detect various data, which is indispensable for fuel supply control and intake airflow control of an internal combustion engine (particularly, an intake pressure sensor to detect an intake pressure to an internal combustion engine), and a throttle system provided with this sensor unit.
2. Description of the Related Art
Recently, an internal combustion engine of an automobile including a motorcycle (hereinafter, referred to an “engine”) has been generally controlled by an electronic control device of an engine on which a computer is mounted.
In an electronic control device of an engine, various sensors to detect operation state or intake state of the engine all the time are arranged at the engine or its peripheral devices, and an electronic control unit (ECU) that electronically performs centralized control of the engine controls the engine optimally based on various data sent from these various sensors.
An engine generates a rotational torque by combusting in a piston, an air/fuel mixture in which a fuel such as gasoline is mixed with air. Therefore, it is important to optimize not only control of fuel supply amount on the engine but also control of intake airflow rate.
In general, an intake airflow supplied to an engine is controlled by a throttle device provided on an intake pipe side connected to an engine. This throttle device controls the airflow by providing a throttle valve inside a cylinder pipe for intake and by adjusting an opening degree of this throttle valve.
Therefore, the ECU needs to accurately detect the opening degree of the throttle valve in the throttle device for intake all the time. The ECU detects this opening degree of the throttle valve based on an output signal from a throttle position sensor (hereinafter, referred to a “TPS”) provided near the throttle valve.
The ECU needs to detect a pressure of air sucked in through an intake pipe for optimal operation of an internal combustion engine in addition to the detection of the opening degree of the throttle valve. In general, such a detection of the intake pressure is performed by an intake pressure sensor provided directly at the intake pipe or at a separate pipeline leading to the intake pipe (refer to, for example, Patent Document 1). When the pressure of the air sucked in through the intake pipe is to be detected by the intake pressure sensor, it is necessary to guide the air in the intake pipe to the intake pressure sensor.
Patent Document 1: Japanese Patent Laid-Open Publication No. H10-512032